cam options for 78 w/base engine
Thread Starter
Cruising
Joined: Nov 2008
Posts: 13
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From: State College PA
cam options for 78 w/base engine
Hi. Newbie from central PA.
Long story short, my uncle bought a 78, 4 speed w/base engine (he says its not the L82).
He wants to get a slightly bigger cam w/ a little lope and do chain/springs/seals this winter. He asks me what I think about a 224/230, .480 SOLID lifter....? I am not well versed in this area. He says solid lifters will give it a better sound. I told him the build may not last as long.? He says he will only drive it 5k miles/year.
I said if he is doing the cam and valve seals he might as well do some heads. Another case of "while I'm in there...." He has 2.5" true duals w/x-pipe and magnaflows and likes the sound now.
First, can someone direct me to the base engine cam specs?
Next, I suspect he just wants an idle to 5500 cam with a little more LSA than stock to create a little lope. Can someone recommend a cam choice or two?
Second, I have read the vortec heads my be a direct bolt on. Is this true? Does a specific year work better or will any 96+ from a 350 do? Would we have to do some considerable gasket matching to get the 78 intake to line up with the vortec heads? Re-drilling required?
I am sure this has been discussed before but I just could not find it in a sticky.
Long story short, my uncle bought a 78, 4 speed w/base engine (he says its not the L82).
He wants to get a slightly bigger cam w/ a little lope and do chain/springs/seals this winter. He asks me what I think about a 224/230, .480 SOLID lifter....? I am not well versed in this area. He says solid lifters will give it a better sound. I told him the build may not last as long.? He says he will only drive it 5k miles/year.
I said if he is doing the cam and valve seals he might as well do some heads. Another case of "while I'm in there...." He has 2.5" true duals w/x-pipe and magnaflows and likes the sound now.
First, can someone direct me to the base engine cam specs?
Next, I suspect he just wants an idle to 5500 cam with a little more LSA than stock to create a little lope. Can someone recommend a cam choice or two?
Second, I have read the vortec heads my be a direct bolt on. Is this true? Does a specific year work better or will any 96+ from a 350 do? Would we have to do some considerable gasket matching to get the 78 intake to line up with the vortec heads? Re-drilling required?
I am sure this has been discussed before but I just could not find it in a sticky.
Last edited by mtsman; Nov 11, 2008 at 04:30 PM.
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
Second, I have read the vortec heads my be a direct bolt on. Is this true? Does a specific year work better or will any 96+ from a 350 do? Would we have to do some considerable gasket matching to get the 78 intake to line up with the vortec heads? Re-drilling required?
I am sure this has been discussed before but I just could not find it in a sticky.
I am sure this has been discussed before but I just could not find it in a sticky.
The Vortec heads are in fact a direct bolt on. The only big issue is the intake bolt pattern is different and the original intake won't bolt on without some extensive modifications to the intake. It's usually easier to buy a Vortec specific intake from the after market.
The other thing to consider are the springs. Keep the cam lift under .420" or you'll need to do some work.
Advanced
Joined: Sep 2008
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From: Union NJ
I would go with the Comp K12-210-2 218/218 duration @.050" .454/.454 lift. I would stay with a single pattern cam for better low end torque. BTW that part # comes with pretty much everything including the chain, springs, retainers, etc. Just no pushrods or rocker arms. I Installed this cam kit with vortec heads on a friends car with very good results.
Thread Starter
Cruising
Joined: Nov 2008
Posts: 13
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From: State College PA
I assume the factory carburator is a Q-jet. Will the Q-jet and all accessories bolt right to a Vortec specific performer (or similar) ?
Last edited by mtsman; Nov 11, 2008 at 04:30 PM.
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
Thank you very much. Do you mean the factory springs on the vortec heads will float if subjected to more than .420? Or, if we changed the factory springs will the factory valve seals allow for more lift than .420? I am kind of a newbie to this.
I assume the factory carburator is a Q-jet. Will the Q-jet and all accessories bolt right to a Vortec specific performer (or similar) ?
I assume the factory carburator is a Q-jet. Will the Q-jet and all accessories bolt right to a Vortec specific performer (or similar) ?
The stock Vortec springs will only be good to .420". However, you can install a spring up to about .470" give or take. Past that you'll have to do work to the heads for larger springs.
The heads have stock size and location accessory holes and the exhaust pattern is the same. The port shape is a little bit different but nothing you would notice.
The intake manifold choices might mean one or more of them lets you bolt on your stock carb. I'm just not sure about that and it has a lot to do with what brand and style you go with.
Thread Starter
Cruising
Joined: Nov 2008
Posts: 13
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From: State College PA
I would go with the Comp K12-210-2 218/218 duration @.050" .454/.454 lift. I would stay with a single pattern cam for better low end torque. BTW that part # comes with pretty much everything including the chain, springs, retainers, etc. Just no pushrods or rocker arms. I Installed this cam kit with vortec heads on a friends car with very good results.
Last edited by mtsman; Nov 11, 2008 at 04:32 PM.
Drifting
Joined: Feb 2005
Posts: 1,738
Likes: 2
From: San diego ca
Get comparison specs here
I've got the 78 L-48 amd L-82 cam specs on my web page. These are the specs provided in teh GM restoration package, so note that the duration numbers are different that the std. advertised or .050 specs. but it should give you a starting point.
I've got the 78 L-48 amd L-82 cam specs on my web page. These are the specs provided in teh GM restoration package, so note that the duration numbers are different that the std. advertised or .050 specs. but it should give you a starting point.
Melting Slicks
Joined: Aug 2002
Posts: 3,334
Likes: 4
From: Midland TX
I would contact your favorite cam company and tell them what you have and what you want. They will recommend a cam for you.
That's what I did on my 72 454 and have been happy with the choice.
A friend picked a cam for his 72 454 just by looking at the specs. His car idled so rough it was unpleasant to ride in. And it didn't develop enough vacuum at idle to raise the headlights or open the wiper door. You had to get out and raise them manually.
Not saying the guys here on CF don't know what they are talking about. They are probably much more knowledgable than me. I would just confirm whatever you choose by asking the company that makes the cam.
That's what I did on my 72 454 and have been happy with the choice.
A friend picked a cam for his 72 454 just by looking at the specs. His car idled so rough it was unpleasant to ride in. And it didn't develop enough vacuum at idle to raise the headlights or open the wiper door. You had to get out and raise them manually.
Not saying the guys here on CF don't know what they are talking about. They are probably much more knowledgable than me. I would just confirm whatever you choose by asking the company that makes the cam.
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Drifting
Joined: Aug 2008
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There really isn't much you can do with a low compression, single exhaust motor. Any cam that is "bigger" than the factory cam is going to be a compromise at some point in the RPM range. If you go 10 degrees bigger, low RPM performance will be degraded, but you will pick up a little on the top end. A general rule is that for every 10 degrees of increased duration @ 0.050 you need to have a compression ratio increase of about 1 point to retain good low speed response. You did not mention the exhaust, but if it is the factory 2 into 1 - 2 out of 1, more cam will net very little if anything.
Thread Starter
Cruising
Joined: Nov 2008
Posts: 13
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From: State College PA
Last edited by mtsman; Nov 11, 2008 at 04:33 PM.
Thread Starter
Cruising
Joined: Nov 2008
Posts: 13
Likes: 0
From: State College PA
There really isn't much you can do with a low compression, single exhaust motor. Any cam that is "bigger" than the factory cam is going to be a compromise at some point in the RPM range. If you go 10 degrees bigger, low RPM performance will be degraded, but you will pick up a little on the top end. A general rule is that for every 10 degrees of increased duration @ 0.050 you need to have a compression ratio increase of about 1 point to retain good low speed response. You did not mention the exhaust, but if it is the factory 2 into 1 - 2 out of 1, more cam will net very little if anything.
Kind of leaning toward a mild cam, vortec head/intake combo. I bet we could make better power and same or better MPG. I think vortec heads are 64-66cc while 78 L-48's are 75cc. If we go vortec, that should increase compression a little. Anyone done the calculations? Feedback?
Last edited by mtsman; Nov 11, 2008 at 04:34 PM.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
Just a note - the stock GMPP Vortecs are good to .475 lift per GM...but that is the absolute max. There are simple swaps that will push the lift out futher, but the stock Vortec flow levels out about about .475-.500...so there's not a lot there past that point.
You really don't want a solid lifter cam on the street - the "sound" he's referring to is the fact that solid lifters are made for high RPM engines, so they have a "lope" at idle. But for your engine they'd be a complete mismatch. If sound is more important than power, CompCams has "Thumpr" cams that have extreme overlap without crazy lift...so they're streetable, but they make less power (and less driveability and fuel economy) than the RIGHT cam for your engine.
A cam in the .450 lift range will do just fine with your stock heads; if you're heading for the Vortecs and can afford it, consider a retrofit roller - the dramatic increase in mid-range lift combined with the mid-range flow of the Vortecs will pay off with some incredible performance for the budget.
You really don't want a solid lifter cam on the street - the "sound" he's referring to is the fact that solid lifters are made for high RPM engines, so they have a "lope" at idle. But for your engine they'd be a complete mismatch. If sound is more important than power, CompCams has "Thumpr" cams that have extreme overlap without crazy lift...so they're streetable, but they make less power (and less driveability and fuel economy) than the RIGHT cam for your engine.
A cam in the .450 lift range will do just fine with your stock heads; if you're heading for the Vortecs and can afford it, consider a retrofit roller - the dramatic increase in mid-range lift combined with the mid-range flow of the Vortecs will pay off with some incredible performance for the budget.
Advanced
Joined: Sep 2008
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From: Union NJ
Thank you Pete. I will check it out. I agree about the singe pattern. I just have no idea what the stock cam specs are so I did not know where to start. Can we reuse the pushrods? Do you have specific rockers you like or used on your friends car? What vortec specific intake did you use and did your Q-jet (assuming) and accessories fit right on?
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 88
From: State of Confusion
Last year, a friend and fellow Forum-member wanted to do the cam/heads/intake swap on his stock L-48 '80 Corvette
http://forums.corvetteforum.com/c3-t...clearence.html
I'd guess he is a 3.55/3.73 gear-swap away from having a 13-second ride, and he seems very-happy with the results.
http://forums.corvetteforum.com/c3-t...clearence.html
I'd guess he is a 3.55/3.73 gear-swap away from having a 13-second ride, and he seems very-happy with the results.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
L48 base motor w/ stock bore
summit K1103 cam&lifter kit
vortec heads
felpro 1094 head gaskets
professional products 52007 intake manifold
static compression will be very close to 9.4:1, usually OE vortecs DO accept up to about .475", 1103 cam (about .443/.465) comfortably under that.
summit K1103 cam&lifter kit
vortec heads
felpro 1094 head gaskets
professional products 52007 intake manifold
static compression will be very close to 9.4:1, usually OE vortecs DO accept up to about .475", 1103 cam (about .443/.465) comfortably under that.
Le Mans Master
Joined: May 2002
Posts: 5,086
Likes: 786
From: Lebanon Township New Jersey
A couple more things about Vortec heads - You will need self-aligning rocker arms. You can get them cheap from GM Perf Parts. Your original pushrods will work. You'll need center bolt valve covers. You can use your Quadrajet with a Edelbrock intake for the Vortec heads with a drop base air cleaner for hood clearance.
Thread Starter
Cruising
Joined: Nov 2008
Posts: 13
Likes: 0
From: State College PA
Last year, a friend and fellow Forum-member wanted to do the cam/heads/intake swap on his stock L-48 '80 Corvette
http://forums.corvetteforum.com/c3-t...clearence.html
I'd guess he is a 3.55/3.73 gear-swap away from having a 13-second ride, and he seems very-happy with the results.
http://forums.corvetteforum.com/c3-t...clearence.html
I'd guess he is a 3.55/3.73 gear-swap away from having a 13-second ride, and he seems very-happy with the results.
Crab is from Scottdale! My uncle is from West Newton. Less than 10 miles from Scottdale! Unbelieveable. Do you think Crab would accept a call from my uncle to talk C3? Should I PM Crab?
Last edited by mtsman; Nov 11, 2008 at 04:35 PM.
Thread Starter
Cruising
Joined: Nov 2008
Posts: 13
Likes: 0
From: State College PA
L48 base motor w/ stock bore
summit K1103 cam&lifter kit
vortec heads
felpro 1094 head gaskets
professional products 52007 intake manifold
static compression will be very close to 9.4:1, usually OE vortecs DO accept up to about .475", 1103 cam (about .443/.465) comfortably under that.
summit K1103 cam&lifter kit
vortec heads
felpro 1094 head gaskets
professional products 52007 intake manifold
static compression will be very close to 9.4:1, usually OE vortecs DO accept up to about .475", 1103 cam (about .443/.465) comfortably under that.
Last edited by mtsman; Nov 11, 2008 at 04:35 PM.
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 88
From: State of Confusion
I'd give Crabby a PM first..... if he hasn't put the '80 away for the Winter, or is busy shoveling snow, maybe he'll show you exactly what his set up looks-like, and/or let you hear it idle.